MDL-38661 Course: Add JS category expander.

This adds a category expanded which:
* fetches child content in a category tree if it has not already been loaded;
* toggles relevant classes on the category node to show and hide child content; and
* applies appropriate animations to improve user experience.
MDL-38661 Add pointer cursor to clickable collapse/expand icons
Automatically generated installer lang files
Automatically generated installer lang files
MDL-38661: Add keyboard support for expansion
MDL-38661 JavaScript: Ensure that ARIA tags are set when expanding/collapsing content
MDL-41570 fixes match qtype's prepare_simulated_post_data

And converts more unit tests to use the method
MDL-41711 Glossary: Fixed seach label alignment
MDL-41717 Theme: Aligned completion checkbox and commands on course page for label
MDL-41728 Backup: Unnecessary use of in_array in base_plan

Remove unnecessary use of in_array which causes performance problems
when loading the plan for very large courses.
MDL-41188 javascript: Change full screen dialogue to position: fixed

This fixes all sorts of bother with the fullscreen dialogues. It also means that
you don't lose your scroll position in the document when the full screen popup
opens/closes.

It prevents several bugs on mobile where the dialogue could get scrolled off
the page (and handles orientation changes better).

Contains one other tiny tweak to make the close button on the dialogue
a bit bigger so it's easier to click (only for fullscreen).
Automatically generated installer lang files
Merge branch 'master' into install_master
MDL-32506 SCORM: remove obsolete setting.
Automatically generated installer lang files
Merge branch 'MDL-38661-m-wip' of git://github.com/andrewnicols/moodle

Conflicts:
	theme/base/style/core.css
	theme/bootstrapbase/style/moodle.css
Merge branch 'MDL-41188-master' of git://github.com/damyon/moodle

Conflicts:
	theme/bootstrapbase/style/moodle.css
Merge branch 'wip-mdl-41711' of git://github.com/rajeshtaneja/moodle
Merge branch 'master_MDL-32506' of git://github.com/danmarsden/moodle
Merge branch 'MDL-41728-master' of git://github.com/sammarshallou/moodle